There is more than one prior apparatus that acts as a warning sensor by detecting fluid level change. Most of these are prone to reliability problems because of their mechanical functionality. An example of a prior apparatus with a reliability issue is one that includes a magnet contained in a float that closes or opens an electrical switch. Another issue lies with ultrasonic sensors, which tend to be relatively expensive. As understood herein, a fluid level warning sensor that works using a vacuum and no mechanical devices to warn when the fluid reaches a low or high level limit thus would provide several advantages in regard to durability, functionality, and cost.